Intel gave up too early in my opinion, the Zenfones (pre-Snapdragon) were great phones, I just don't think Asus alone had enough penetration to make it worth their while.
My experience with the Zenfone 2 was not very positive though. It seems to have been more Asus's fault than Intel's, but also Intel could have done a better job with their kernel. Yes the CPU was fast relative to its price (because Intel was dumping them) but almost everything else about it was not very good. Battery life was poor, seemingly because Intel never got core parking to work in their Android kernel (I also owned a Lenovo Atom tablet which had the exact same problem so I'm going to blame Intel here). Most apps ran pretty fast but anything with ARM binaries ran very slowly in emulation or in a few cases didn't work at all. ASUS's Android skin was terrible and had an obscene amount of preinstalled bloatware. There were loads of bugs, and installing updates was always a guessing game of whether it improved things or made it even worse. Sometimes GPS wouldn't work. The Marshmallow update was both extremely late and extremely buggy. The plastic back started developing cracks after about a year without ever dropping it.
The ability to run windows software in either Wine or a VM was a rather cool-but-useless novelty.